Image sensors are used in imaging devices such as digital cameras. Semiconductor-type image sensors are fabricated from silicon and are commonly arranged as a two-dimensional array of pixels (i.e., CMOS pixel array). During the semiconductor fabrication process, defects may occur in some of the pixels of the image sensor. Defective pixels used in an imaging device may result in visible defects in a processed image such as a bright or a dark spot in the processed image. The pixel with the defect is referred to as a “bad” pixel. Because the bad pixels appear as visible defects in the processed image, it is not desirable for an imaging device to use image sensors with bad pixels. Thus, the cost of manufacturing image sensors increases because only image sensors fabricated without bad pixels are available for use in imaging devices.
Given this high cost of manufacturing, there have been some attempts at using image sensors with bad pixels. For example, one attempt calibrates each image sensor during a final production test. The final test examines the pixel array and tests for bad pixels, storing the coordinates (i.e. row and column number) of the bad pixels in a programmable read only memory (PROM). The PROM may either be integrated into the image sensor device or may be shipped as a separate PROM. An imaging system may then use the information stored in the PROM to determine which of the pixels in the image sensor are bad and discard the outputs generated from those pixels. Interpolated outputs are generated to compensate for discarding the outputs of the bad pixels. The imaging system will generate each interpolated output value based on the output of pixels located near the bad pixel (i.e. adjacent pixels). This attempt, however, is very expensive because it requires the use of a PROM and an exhaustive calibration cycle during final test.